This invention relates a method of preparing a color hologram.
It has been known for a number of years that the best color reproduction from three monochromatic color sources requires the wavelengths of 450 nm, 570 nm and 610 nm (See Journal of the Optical Society of America Volume 61, Number 9, page 1155, W.A. Thornton). This is also true of three color holography. However lasers which emit at these wavelengths are not readily available. We have found a method of Preparing a three color hologram in which the colors are reproduced as if lasers emitting at the above wavelengths had been used but by using more readily available light sources.
Various background prior art is known to us, for example, that of Japanese patent No. JP-A-58 184 985 (as described in Patent Abstracts of Japan Volume 8 No. 31 (P-253) and that of Japanese patent No. JP-A-54 17 865 (as described in Patent Abstracts of Japan Volume 3, No 38 (E-101) and also European patent No. 128,033, British Patent No. 1316677 and U.S. Pat. No. 4235505. However none of this prior art relates to the problem which it is the object of this invention to solve.